| 摘要 |
PURPOSE:To avoid the generation of excessive torque on change-over since an inverter is made work as converter for the change-over from Scherbius operation to secondary short-circuit operation. CONSTITUTION:The firing angle of the thyristor of an inverter 4 is controlled by a phase control circuit 10-3 and limited by a phase limiting circuit 10-6 so that control advance angle gamma may not exceed 90 deg.. On the change-over from Scherbius operation to secondary short-circuit operation, control advance angle gamma is made larger than 90 deg. by stopping the function of the circuit 10-6, and the inverter is made work as converter. Then, the current of the inverter 4 becomes the circulating current if passing through the arms of the commutators 2 and, if the current if is larger than the secondary current i2 of a motor 1, all the commutators 1 make continuity. Thereby, the fall component of voltage can be compensated and the same speed as obtained when the secondary short-circuit magnetic contactor 7 is shorted can be developed. Change-over can thus be performed without generating any excessive torque. |
